Polar stratospheric clouds - or nacreous clouds - are pastel-hued iridescent clouds located in the stratosphere which can usually be seen at high latitudes. They form at altitudes of 15,000 to 25,000 metres and are pretty rare to see, especially in the UK.
An interesting fact about the etymology of "nacreous" is that "nacré" translates in French to "mother of pearl" - which perfectly describes the colour and appearance of these beautiful clouds.
Nacreous clouds form when stratospheric temperatures drop below -78C and when the air is filled with ice crystals; so when the sun's rays shine through we get to see this pearlescent show of colours.
Earlier in the year, we were lucky enough to see some of these rare and beautiful clouds in the North East of England.
Click on the photos below to see more.
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